R (2002): Physiology of the auditory afferents in an acoustic parasitoid fly

The fly, Ormia ochracea, possess a novel auditory organ, which allows it to detect airborne sounds. The mechanical coupling of its pair of tympanal membranes provides the basis for a unique means of sensing the direction of a sound source. In this study, we characterized the neuroanatomy, frequency tuning, and neurophysiological response properties of the acoustic affer-ents. Our experiments demonstrate that the fly’s nervous sys-tem is able to encode and localize the direction of a sound source, although the binaural auditory cues available in the acoustic sound field are miniscule. Almost all of the acoustic afferents recorded in this study responded to short and long sound pulses with a phasic burst of one to four action poten-tials. A few afferents responded tonically for the duration of the sound stimulus. A prominent class of afferents responds to suprathreshold stimuli with only a single spike discharge, inde